U.S. Pat. No. 7,026,701 teaches rectangular type surface plasmon waveguides and buried rectangular surface plasmon waveguides for use in Schottky barrier detectors. These surface plasmon waveguides suffer from polarization dependence and fringe fields at the corners of the waveguides. To achieve amplification of the detected signal, such detectors require external amplifiers, which increase noise, reduce bandwidth, and increase system complexity
The phototransistor, which is a photon-actuated transistor, is also well known in the art. Recent work has been done on phototransistors that are compatible with commercial silicon BiCMOS processes. These devices, however, are generally slow in frequency response due to the large area and thick base region. This is a fundamental limitation of these devices due to a mismatch in dimension between optical waveguides and semiconductor transistors within an integrated circuit. Diffraction will not allow micron-scale optical signals to be routed directly to nano-scale transistors.
Digital systems using conventional semiconductor technology are inherently low-bandwidth as compared to optical communications and processing of information in the optical regime. A fundamental problem currently facing microelectronic circuits is that intrachip and interchip metal interconnects cannot keep pace with the transistors in terms of bandwidth and latency. While the transistor is improving with each successive generation of lithography, the performance of the metallic interconnects degrades significantly when scaled down in size. Optical interconnects can resolve most of the physical issues, but optical interconnects are limited in size to dimensions on the order of the wavelength. Unfortunately, these sizes are orders of magnitude larger than those on the active region of modern semiconductor chips.
Conventional interconnects suffer from relatively low bandwidths as compared to the optical regime. The size of conventional phototransistors limits their frequency response and dark current. Plasmon waveguides suffer from polarization dependence and fringe fields limiting use in semiconductor devices. These and other disadvantages are solved or mitigated using the invention.